The next song contains first and second endings. The first time you play through the song, play the first ending Z then go back to the beginning. The second time you play through the song, play the second ending X instead of the first.
Congratulations on finishing the book. Here is a 12 Bar Blues solo to learn and enjoy. Learn each hand separately before putting them together. Take care with the fingering and practice the piece slowly until you can play it perfectly. It is recommended that you now move on to Progressive Keyboard Method for Little Kids Book 3 .